This invention relates to the field of battery charging circuits, and, more particularly, to the provision for a warning indicator when the power source overheats.
In the field of battery charging devices, including alternators and regulating circuits, it is well known to use a thermal switching element which will open the circuit of the field coil when the device overheats. In one such device, a lamp is turned on if the thermal switch is activated but, in this circuit, the lamp is put across the supply and thus requires the use of a rather expensive large resistor in series with the lamp. In another device for providing relief for an overheat condition in large motor windings, a thermal switch is coupled to a bimetallic element positioned within the windings. WHen the switch is closed, it completes a circuit including a lamp, a siren and a resistor plus, if desired, a stack of carbon disks with resistance which decreases as the temperature goes up. None of the known arrangements provide for a separate warning lamp to indicate only a overheat condition. Overheating is particularly a problem in alternators operating in an excessively dusty environment; for example, in a tractor during harvest time.